1. Field of the Invention
The disclosure relates to a sniffing leak detector comprising a main device including a vacuum pump apparatus generating a high vacuum, and a gas detector, and a hand-operated sniffing probe connected to a gas inlet conduit of the main device via a flexible sniffing hose, and a detachable hose coupling.
2. Discussion of the Background Art
In leak detectors of the type designed for sniffing operation, the gas taken up by the sniffing probe is conveyed via a sniffing line to the main device. Within the main device, the concentration of the test gas in the sucked airflow is measured with the aid of gas detector, e.g. a mass spectrometer. For analysis, only a small portion of the gas is admitted into the high vacuum where the gas analysis is performed by means of the mass spectrometer. The bulk of the gas flow is pumped directly back into the atmosphere by a forevacuum pump. Normally, the forevacuum pump also generates the low fore pressure for the turbomolecular pump that generates the high vacuum for the mass spectrometer. For obtaining a sufficiently low fore pressure as well as a defined gas inflow into the high vacuum system, it is required to throttle the gas flow. This throttling is normally effected by the flow resistance of the sniffing line, which results in a pressure drop. Sniffing leak detectors are operative with a gas throughput between 20 sccm (standard cubic centimeters) and 300 sccm, depending on the type of the device. In case that, during operation, the sniffing line is detached from the main device, e.g. for replacing a clogged line by a new one, the pressure in the gas inlet conduit will increase to approximately 1000 mbar. This will cause a considerable pressure increase in the high vacuum region, which may lead to destruction of the gas detector or the vacuum pump apparatus. Thus, as result of a pressure increase, the emission filament of a mass spectrometer may be destroyed, with the consequence of total functional failure. Also by a pressure increase in the forevacuum system, a turbomolecular pump is subjected to a considerable stress because, with the sniffing line detached, the pump has to work beyond the admissible specification.
It is an object of the disclosure to provide a sniffing leak detector which is insensible to detachment of the sniffing hose from the main device in that the endangered components are protected from a too massive gas flow.